The present invention relates to a device, system and method for determining the position, in particular for example the spatial position or the position relative to a system of co-ordinates, or for positioning or preparing the positioning of a medical operating instrument, an incision block or a bone or part of a bone.
When attaching implants, such as artificial knee, elbow, finger or hip joints, it is required that the implant, such as a joint or part of a bone, is positioned as accurately as possible onto the adjacent bone. For this, the most accurate possible incisions must be made to the bone structures adjacent to the joint. FIG. 8 shows in diagram form the positioning of an incision block 1 onto a femoral bone, in accordance with the prior art. For this purpose, a guide rod 100 is inserted into a bone K, a positioning mechanism 101 being provided at the external end of the guide rod 100 for positioning and holding the incision block 1 in a desired position. Once the incision block 1 has been placed in the desired position, then positioning pins 3, for example screws, nails or pins, may be inserted into the bone K through holes 2 provided in the incision block, to fix the incision block 1. Once the incision block 1 has been fixed onto the bone K, a first incision plane S0 can be made, preferably as vertically as possible or at a slight angle to the mechanical axis of the bone, by means of a cutting tool 4, as shown in diagram form in the FIGS. 4A and 4B. In the example of the femoral bone, additional incisions must be made in additional planes S1 to S4, running obliquely or at an angle to incision plane S0 as shown in FIG. 6, in order to be able to position the corresponding knee implant component onto the bone. For this purpose, a second incision block 10 is placed on the first incision plane S0 and positioned by means of a suitable mechanism, further lateral incisions being made to the bone K with said second incision block 10, by guiding the cutting tool 4 into the obliquely running or lateral slits of the second incision block 10.
It is the object of the present invention to propose a device, a system and a method for determining the position of an incision block or a medical operating instrument or a bone or part of a bone, whereby this determining of position is simplified.
This object is solved by the features of the independent claims. Advantageous embodiments arise from the sub-claims.
The device in accordance with the invention for determining the position of an incision block, in particular for a surgical method such as for example the creation of one or more incision surfaces for an artificial joint, comprises a positioning element with at least one reference point, whose spatial position can be detected. The positioning element can be either active and/or passive elements which output and/or reflect suitable signals which are detected by corresponding recording devices, such as for example cameras, in order to be able to determine the spatial location of the positioning element and the device connected to it. Furthermore, the device in accordance with the invention is provided with a position determining element, allowing the position of an incision block on a bone to be determined directly or indirectly.
If the spatial location of the bone or of another body structure is known, then the relative location to the bone, for example, can be determined, and a device placed in a desired position on the bone, based on this information. This procedure is generally referred to as xe2x80x9cnavigatingxe2x80x9d.
In a first embodiment of the invention, a connecting element is provided on the device in accordance with the invention as a position determining element, which may be placed in a defined positional relationship to the incision block to be positioned, and connected with and/or attached to it. This may be one or more plate-shaped elements, for example, wherein at least one of these plate-shaped elements can be inserted, for example, into the guide slit of an incision block, in order to place and/or navigate the incision block into the desired position on the bone, in which an incision can be made in the desired plane by guiding a suitable cutting tool through the guide slit located in the incision block, preferably after fixing the incision block on the bone and removing the device in accordance with the invention. In general, however, other connections between the device in accordance with the invention and the incision block are also possible, as long as a desired, defined positional relationship between the device in accordance with the invention and the incision block is maintained, and as long as it is possible to navigate the cutting plane defined by the guide protection to the desired point.
If plates, or pegs lying in a plane, are used which can be inserted into a guide slit of the incision block, it is advantageous to provide a number of plates or pegs which preferably lie in a plane and have different thicknesses or diameters, in order to be able to insert these plates or pegs into guide slits of differing widths into the incision block.
In general, if the positional relationship between positioning element and connecting element is known, the connecting element can be arranged on the device in accordance with the invention, for example shiftably, or rotatably about an axis. If, for example, plates are used for insertion into the guide slits of an incision block, then the incision block can be exactly positioned in the desired plane, even if the plates are rotated or shifted, since the rotation of a plate about an axis parallel to the vertical of the plate surface can also be interpreted as shifting in a plane, and since the incision block is to be positioned accurately with reference only to the desired incision plane which in theory can extend infinitely. A shift of the incision block which does not alter the incision plane defined by the guide slit in the incision block is therefore insignificant.
In accordance with the first embodiment, an incision block can therefore be positioned by correctly aligning the desired incision plane, i.e. by navigating the incision plane and/or the guide slit of the incision block. This way of positioning an incision block is preferably used for positioning the first incision block as shown in FIGS. 4A and 4B, for cutting a plane preferably perpendicular or at a slight angle to the mechanical axis of the bone.
In accordance with a second embodiment of the invention, which may be used in combination with the first embodiment or separately as an independent, individual embodiment, a device for preparing and/or creating a connecting structure between the bone and the incision block may be used as the position determining element.
This device for preparing or creating a connecting structure can for example be a hole template and/or a fissure template with at least one through hole or fissure defined by the template, which is placed in the desired position, for example on a bone, using the positioning element connected to the template. Guide holes are provided in the hole template, which may be used for drilling holes in the bones or for inserting suitable connecting elements into the bones, for example pins, nails or screws. Guide fissures are provided in a fissure template, which may be used for sawing or fraising slots or fissures in the bones or for inserting suitable connecting elements into the bones, for example plates. A combination of hole temple and fissure template is also possible. A second incision block, such as for example the second incision block illustrated in FIG. 6, can be attached to or slipped onto on these connecting structures prepared with the aid of the template and/or these aligned connecting elements, such as for example holes drilled with the hole template. The position of the second incision block is thus determined only indirectly through the template, for example the hole template, as opposed to the first embodiment. In general, however, the first or the second incision block can be directly or indirectly positioned.
In this way, the template can be shifted, for example, on the first plane S0 created with the aid of the first incision block, and need only be shifted into a desired position on said plane S0, complete navigation in three-dimensional space not being required. However, such three-dimensional navigation of the template to the desired place may also be carried out.
Fixing elements on the bearing surface of the template, for example spikes, may serve to fix the template on the already created plane S0, which can be pressed into the soft structure of the bone tissue by applying a gentle pressure on the opposite side of the template.
A reference star with three passive markers arranged on it is preferably provided as the positioning element, preferably comprising a first geometry for navigating the first embodiment by inserting a small plate into a guide slit of the incision template, this geometry preferably being different to the geometry and/or arrangement for navigating the hole template of the second embodiment. In this way, the reference stars can be clearly assigned to the elements navigated by these reference stars respectively.
The system in accordance with the invention for determining the position of an incision block consists of the device above described and the incision block itself, as described in the first embodiment, or of the device above described and a device for preparing and/or creating a connecting structure, such as for example the hole template described in the second embodiment.
Suitable positioning elements, such as for example a reference star, are also preferably provided on the body structure to be treated, for example on a bone which is to be incised, in order to be able to exactly navigate these devices from the spatial positional information acquired in this way, in combination with the positional information of the guided incision block or of the hole template.
In the method in accordance with the invention for determining the position of or for navigating an incision block, the position of the positioning elements attached to a body structure, for example to a bone, is firstly determined, from which the spatial position of, for example, the bone or a joint may be determined. Moreover, the spatial position of the positioning elements of an incision block or of a hole template is determined, such that the relative positional relationship between the body structure, for example the bone, and the incision block or hole template can be determined from these two items of positional information. Based on this relative position, the incision block or hole template may be navigated to a desired place. For this, suitable display devices can be provided which show the relative positional relationship.